ALL space agencies of the world are (FIRST!) "governmental (then, bureaucratic) agencies" that (also) works under a very high political influence, then, it's impossible to change their (good or bad) decisions without the political support of the country/countries that lead the agencies.

Also, if engineers and scientists suggests something of useful or remarks a (possible) mistake/risk, the (bureaucratic) agencies go across their ways they like a train on its rails!

And (you know...) it's easier to move a mountain than change the decisions of a bureaucratic agency (of whichever kind and/or country).

Then, all forums' discussions about NASA/ESA plans are only an interesting (but useless) "intellectual game".

However, since I like to play that "game", on my website's articles and forums' posts I suggest many possible changes and alternative missions' architectures.

In this thread I explain another problem that may happen with the ESAS vehicles when the moon missions will start in 2020 (latest official date).

The problem is that (I think) the CaLV is TOO LITTLE for ALL future evolutions of the ESAS missions!

Of course, NASA will design a CaLV with sufficient payload to accomplish the moon missions, but, with its low payload limits, NO EVOLUTIONS WILL BE POSSIBLE.

Develop and build the CaLV will need 15 years of time and $10+ billion of funds, then, when it will be ready to fly (in 2020) NO CHANGES will be possible to the rocket and its payload without spend many extra years of time and extra billions of funds!

If better and bigger Moon/Mars vehicles will be designed in next 20 years, they can't be built nor launched because the ONLY big rocket available in 2020 will have no sufficient force to launch them!

Just imagine that NASA is (now) a family of four persons (father, mother and two sons) that buy a four-seats car for their travels.

Clearly, the four-seats car is (now) sufficient for four persons... but the family may grow in nexts years... with more sons, parents, etc. to travel... and the family may need an eight-seats car!

Well, while it will be (costly but) easy for a family to sell the little car and buy a bigger vehicle, it will be not so easy for NASA to build another (bigger) CaLV when they discover that the planned CaLV is too little for better and bigger Moon/Mars missions!

Then, my suggestion is to develop and build a BIGGER rocket than CaLV since its R&D time&costs don't change so much with a 125 mT or a 200 mT CaLV (and also the extra-hardware-costs are not so much) but, while the 200 mT CaLV can be used for BIG and LITTLE payloads, the 125 mT CaLV can be used only for LITTLE payloads ...and BIG payloads will need TWO rockets ...that costs MORE (time and money!) than, simply, add two SRBs to the standard CaLV!

My suggestion is to build the CaLV with FOUR 4-segments "dumb" (Shuttle-standard) SRBs, up to SIX main engines (SSME or RS-68) and TWO J-2x (instead of one) for the 2nd-stage/EDS.

I think that a CaLV like this may launch up to 200 mT payload for BIGGER and BETTER missions!

I dont think Nasa has enough money to build CaLV in the time period it wants to, making a bigger launch vehicle will just push it out even further and will probably mean it dosent get built at all.

using your analogy, nobody buys a people carrier when all they need is a saloon. Personally as far as manned spacecraft are concerned I would prefer to see small craft (less than 10 tons) able to carry 6 or more astronauts launching on a variety of different boosters on a regular basis.

_________________A journey of a thousand miles begins with a single step.

if and when it is looked at and called for HLLVs etc. it can, should or must be asked where the maximum is and it seems to turn out that there is no maximum - it's allways possible to call for more payload capacity in units of weight. The desires tend to grow and to grow and there is no end of it - this is one essential reason why budget constraints are felt and why larger budgets are called for.

Another point is why regarding transportation across the earthian surface such vehicles aren't called for. Of course - across land and rivers nature and environment set boundaries everyone easyly understands and accepts. But across the oceansthese boundaries don't exist - but the claims aren't there. There only is a tendency of ever growing capacities of ships which is due to economies of scale - but these economies merely have to do with reusability and thus trip rate. If ships weren't reusable the large capacities would be uneconomical.

Regardless what someone has in mind to do on the Moon, on Mars or elsewhere in space it should be done like it is done on Earth - by several transportation trips and building and constructing it step by step. Then it can be started earlier, continued permanently and includes flexibility for correction of errors, mistakes, new developments and optimization - which all is required for projects taking that long time a lunar station and even the return to the Moon requires.

Regarding the Shuttle it is correct that assembly tools, crane/robot arm etc. are required for in-space assembly as it is done at present - but they all don't need to be mounted, attached or so to the Shuttle. In principle no payload needs a cargo-bay to be transported. It would be sufficient if a rocket releases the payload in orbit, a vehicle consisting of the engine(s) and the tank(s) only approaches, docks to the payload or catches it and then moves it to the ISS, an assembly yard or anything else - that vehciel then would be a tug-boat.

Because of the comparison-thread in the Technology section and some threads in the Financial Barriers section there is no guarantee that fewer launchers mean less costs - it may be reverse. At least there is a critical point where the relation changes to the opposite. As long as this critical point isn't achieved the bigger CaLV means more costs.

no, they are more economical since a big rocket shares its R&D costs on twice the payload per launch

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...taking that long time a lunar station and even the return to the Moon requires...

big projects need time, but a small-CaLV will become inadequate a few years after its first launches, when NASA needs will grow

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...no payload needs a cargo-bay to be transported. It would be sufficient if a rocket releases the payload in orbit, a vehicle consisting of the engine(s) and the tank(s) only approaches, docks to the payload or catches it and then moves it to the ISS, an assembly yard or anything else - that vehciel then would be a tug-boat...

If you review the Airbus 880 development effort, you will note that R&D for a large aerospace vehicle is much larger than for a smaller vehicle.

(The uncertainties and risks are also greater).

You may know how to develop a vehicle with far greater mass without increased costs, but the rest of the world hasn't learned how. In point of fact, the assumption that R&D costs increase little with an expanded project lies behind a great many development budget blowouts!

The big benefits from scale result from a smaller flight crew (IF THESE COSTS ARE SIGNIFICANT). Development and Production costs are remarkably flat as costs per kilogram of vehicle. You may want to immagine that this is not so, but a century of data argues that it is.

What is called "Economy of Scale" usually relates to PRODUCTION QUANTITY! Making several products of the same design reduces the unit cost. (Twice as many vehicles produced most certainly "dilutes" the development cost). Typically, doubling production cuts costs by 20%, which in the real world, is a significant competitive advantage.

If you review the Airbus 880 development effort, you will note that R&D for a large aerospace vehicle is much larger than for a smaller vehicle.

that is true (in part) for a big (and completely new) airplane like the Airbus, not for the CaLV

the CaLV already is a big rocket that need $10+ billion of R&D... increase its payload capacity will cost many billions if NASA must modify the standard CaLV after 2020... but may cost a few millions (or nothing) if NASA build ONLY the biggest rocket

if you see the early ESAS drawing of the CaLV, you discover that it was planned to have four OR five main engines and TWO 2nd stage (J2S) engines

the only difference to build a 200 mT CaLV is to add a sixth RS-68 and four 4-seg.SRBs instead of two 5-seg.SRB

and, since the 4-seg.SRB are READY AVAILABLE (and don't need 3 years and $3B of R&D...) the big-CaLV will cost LESS than its smaller brother!

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uncertainties and risks are also greater

like with ALL (little and big) rockets... and that don't change so much if it is the SaturnV or the small-CaLV or the big-CaLV

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...far greater mass without increased costs...

as explained, the big-CaLV will cost an extra $150M of hardware but not of R&D

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What is called "Economy of Scale" usually relates to PRODUCTION QUANTITY! Making several products of the same design reduces the unit cost. (Twice as many vehicles produced most certainly "dilutes" the development cost). Typically, doubling production cuts costs by 20%, which in the real world, is a significant competitive advantage.

true, but the price reduction is sensitive only if we talk of "thousands" (like airplanes) or "millions" (like cars) NOT with the CaLV

the number of CaLV built and launched in 2020-2025 will be ONLY 15, no matter if they will launch 125 or 140 or 200 mT payloads

the difference will be NOT the price but (only) that with a big-CaLV many (better & bigger) payload may be launched... like a Lunar Space Station, big tanks to refuel reusable-LSAMs, a new (28.5 degrees) ISS built with two launches, big Moon Crew Habitats, pressurized rovers, etc.

rpspeck is completely right and argued like Economics do. I explained the links and connections in the Financial Barriers section in the theoretical Costs-thread as well as in the scientific estimation-thread.

The point regarding large CalVs is that the amount of cargo is limited each point of time. This limited amount is the total capacity the market or what might be called its substitute is demanding. Logically the larger the CalV the less the number it is required by - and/or the less the required number of flights of a reusable CalV. This in turn logically means that the production quantity (rpspeck) demanded is the less the larger the capacity of the CalV. And this means that the economies of scale by number of vehicles or by number of flights can't be achieved.

So what's left is to what degree the capacity alone vehicle results in economies of scale. The higher the hardware costs the less the economies of scale of this capacity compared to number of vehicles or number of flights.

This all results from mathematics and logics.

But there is a factor limiting the degree the capcity can be used by. The larger the capacity the more cargo is required to get economies of scale and to achieve the critical point where the degression of costs results in economical advatages over other vehicles.

This turn means that the time between two launches is the longer the larger the vehicle and the larger the payload to be gatheres in it. This again has its impacts - avoidable delays in station construction. The construction nees only a few payloads per unit of time to go on - so if all the units are to be gathered over a longer period of time than needed to do construction by a few payloads then there is an avoidable delay.

Delays mean increased costs because they cause unemployment of astronauts being on the Moon and of equipment installed on the Moon (can be replaced by ISS, orbit etc.)

Delays have to do with workflow - and the vehciels have impacts on the workflow. The workfow is what has to be organized and the CalV has to fit into the workflow.

This all together with what is known about the Bush-plan and NASA's approach(es) to make that plan reality means that larger CalVs urgently should be avoided because they would increase the costs of the project which are already calculated to be $ 104 bio. Each percent increase is an increase by $ 1.04 bio and more.

The work to be done on the Moon in principle requires a management like that of private companies because such managers are familiar with what I explained.

By the way - the delays also mena the high risk of increasing costs by mismanagement and inflation.

Another point is that while it may be relatively easy to find smaller payloads, large 200 ton payloads are few and far between.

Gathering together a group of smaller payloads into one big one is not always a good idea because of time delays for individual loads and overall loss in payload capacity due to the need for extra rocket infrastructure to mount and launch them.

_________________A journey of a thousand miles begins with a single step.

in the short term (if we can call the next "20 years" a "short term"...) the number of CaLV is set by the number of planned launches (about 15 test/moon missions in 2020-2025)

then, I don't see any "scale economy" in a 15-units-only production... the CaLV is not a mass product

as I've explained, the big-CaLV may cost the same (or less, thanks to its ready available 4-seg.SRBs) than a small-CaLV but, while the big-CaLV may launch better and bigger payload (like better and bigger lunar modules) the "small" may accomplish ONLY the planned-weight moon missions...

no space for upgrades... no space for changes... no space for different vehicles... no space for new ideas... only the "standard" moon missions for 20+ years!!!

only when the CaLV will be built in 50+ units, the "scale economy" may have some influence... but... when we will see the CaLV #50 launch? 2040...? 2045...?

many say that it will be "the rocket for Mars"... but I don't think that... Mars missions will not use the CaLV nor the CEV... but some, completely new, vehicles... and 30+ years from now are too much to have the opportunity to imagine these new vehicles!

the (small or big) CaLV will NEVER enter the "scale economy age" like we know also for high priced products

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...all results from mathematics...

of course, the common evaluations about scale economy are true for all other rockets built in hundreds units... the Soyuz/Progress are low priced (also) thanks to scale economy

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...larger the capacity the more cargo is required to get economies of scale...

true, but the extra-cargo will NEVER be a "dead weight"

if you send more supplies, they will be used... if you send two more rovers, they will be used... if you send more tools, they will be used... nothing will be lost with a bigger-CaLV

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...turn means that the time between two launches is the longer the larger the vehicle and the larger the payload to be gatheres in it...

not true, the number of launches is limited only by funds available

why NASA will launch two moon missions per year?

why not one, or five?

the answer is not "scale economy" or "too big rocket" but only "FUNDS"

give NASA sufficient funds and they will launch TEN small-CaLV per years or TWENTY big-CaLV per year!

q: why, after dozens Shuttle launches, the ISS is so little?

a: funds!

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...Delays...

unfortunately, great part of delays will not come from rockets' dimensions...

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...larger CalVs urgently should be avoided...

I don't suggest to build the Star Trek Enterprise!

ONLY to add 2 SRB, 1 RS-68 and 1 J-2x to the standard CaLV

I'M SURE that, if "my" big-CaLV was the CaLV that NASA included in the ESAS plan six months ago, NOW, nobody may say: "it's too big!"

it's appear a bad idea only because it's not an official NASA idea!

but, if NASA will say: "...since the difference is not so much we decided to build a 200 mT version..." all peoples will say: "very good! great idea! it's right! NASA is ok!" etc. etc. etc.

and (believe me!) ...NASA will change its CaLV specs in the next 15 years while develop and build it!